Reduction of ear-position sound pressure at low speed in electric vehicles by pulp mold (Translated)

Electric vehicles (EVs) produce different cabin noise than internal combustion engine (ICE) vehicles during low-speed driving. To identify the cause of the interior noise of an EV at low speed (30km/h) and to reduce it, a Helmholtz resonator made of pulp mold was fabricated, and its noise-reduction effect was evaluated. First, a Helmholtz resonator is investigated numerically to reduce the tire's cavity resonance. Numerical calculations demonstrated that a stable noise-reduction effect could be achieved by installing multiple Helmholtz resonators. Next, we fabricated a Helmholtz resonator using a pulp mold and installed multiple resonators in the tire. In the experiment, the resonators reduced the tire cavity resonance by 13.8 dB to 9.7 dB. When driving tests were conducted with these tires installed, noise at the front-seat ear positions was reduced by 11.3 dB. From these results, we identified that tire cavity resonance is the cause of cabin noise at low speeds. In addition, a driving test in which the same number of Helmholtz resonators as installed in the tires were installed on the cabin ceiling resulted in an 8.1 dB reduction in cabin noise. We demonstrated that it is possible to reduce tire cavity resonance noise, even with parts inside the vehicle.